Another thing is that you have an extra frame that can be put onto Draguns/spyders and up the bps a lot. I personally think that having the extra original frame makes a nice upgrade to any blowback out there(other than FF draguns) and should be considered into the cost of the one kit if you have an extra blowback around. You have two ripping guns now and not just one.
yeah what i really mean is that many upgrades you go from a crappy part and never use it and put on a nice part. You can still use the crappy part but you wont. In this case you get a new great replacvement and a great old part. I just realized it the other day about buying the one kit and a tes and putting the extra parts on an old compact(spyder). That would take one good gun and make it somewhat better and also take a crappy gun and make it really nice. This is an added benefit with the one kit but no it isnt specific to the TES improvements.